The four-wheel drive feature on certain motor vehicles is a power transfer system that allows the vehicle to be driven by all four wheels, resulting in improved traction and control of the vehicle. Some types of four-wheel drive vehicles include a driveline which is equipped with a transfer case. The transfer case allows both the front and rear axles to be driven. Particularly, the function of the transfer case is to transfer engine torque from the transmission to the relevant propeller shafts which extend to both the front and rear axles.
Typically the four-wheel drive feature of such vehicles is operable via an auxiliary switch or a manual shifting by which the front-wheel drive can be engaged and disengaged at will. All-wheel drive (AWD) is a variation of four-wheel drive which shifts automatically during the appropriate driving situations, instead of requiring the operator to manually shift as in four-wheel drive. Because the propeller shafts which extend to each axle are continually moving with respect to each other, the transfer case is normally located in the mid-point area of the vehicle in order to provide service to both axles.
The driveline of a typical four-wheel drive vehicle also includes a slip joint between the propeller shafts and the transfer case which serves to accommodate the changes in distance between the axles and the transfer case as the front and rear wheels move up and down during operation of the vehicle. The slip joint is used to lengthen or shorten the propeller shaft and is typically a splined shaft coupling such as a universal joint of the cardan type. Proper alignment of this type of universal joint in conjunction with its attached coupling, such as the transfer case, is desirable. Such alignment is particularly desirable because improper or incorrect positioning of the splined shaft with the mating splines of the coupling may result in noise, vibration and harshness in the joint and in the overall assembly. Misalignment may also result in undesirable forces therebetween.
Consequently, a need has developed for an improved connection between a slip joint and its mating coupling, in order to reduce any noise, vibration and harshness in the assembly. There is a further need to improve the connection between the splined universal joint shaft to the adjoining coupling. The improved connection should also provide for a better and more efficient torque transmittal generally between mating splined components.